Transport of vitamin B12 in Escherichia coli: common receptor system for vitamin B12 and bacteriophage BF23 on the outer membrane of the cell envelope

Abstract

We showed previously that the outer membrane of the Escherichia coli cell envelope normally contains about 200 to 250 B12 receptors, and that these receptors function both in B12 transport and as receptors for the E colicins. This paper shows that this receptor system is also shared with bacteriophage BF23. A strong positive correlation was observed between the number of B12 receptors per cell and the rate of adsorption of BF23. Cells from mutant strains that lacked B12 receptors did not adsorb BF23 particles. The rate of adsorption of BF23 to cells of a merodiploid strain (RK4151), with about 550 B12 receptors per cell, was approximately double that to cells of a nonnal, haploid strain. The adsorption of BF23 to whole cells, cell envelopes, outer membrane particles, and solubilized outer membranes was inhibited by vitamin B12, with 50% inhibition at B12 concentrations in the range of 0.5 to 2.0 nM. These values are close to the 1032 on August 5, 2020 by guest

Pores in the outer membrane of Escherichia coli K12. Involvement of proteins b and c in the permeation of cephaloridine and ampicillin

“…In Escherichia coli uptake of complexed iron ions is mediated by various outer membrane proteins [1][2][3]. The products of the genes bfe, lamB and tsx are involved, respectively, in the uptake of vitamin B12 [4,5], of maltose and maltodextrins [6,7] and of various nucleosides [8].…”

Receptor uptake arrays for vitamin B12, siderophores, and glycans shape bacterial communities

“…Escape from attack Colicins and phage use corrinoid receptors as a point of attack (Bradbeer, Woodrow, & Khalifah, 1976;Di Masi, White, Schnaitman, & Bradbeer, 1973;Kadner & Bassford, 1977). Colicins are toxins secreted by bacteria that can kill other bacteria.…”

Studies on the gene for the multivalent vitamin B12 receptor of Escherichia coli

“…At least 12 different ligands, some of which are closely related, bind to the BtuB protein. In doing so, they exhibit competitive binding kinetics in that interaction with one ligand prevents the binding of a second [3,4]. These characteristics of the vitamin B12 receptor, and the fact that intracellular utilisation of cobalamin can be readily assessed through the use of vitamin Blz-requiring strains, makes the BtuB protein particularly amenable to genetic and biochemical analysis.…”